A virus that comes within an file attached to an email message. When that file is opened, the virus does its damage. Macro viruses can come in Microsoft Word documents that are sent as email attachments. The macro causes the damage when the document is opened providing macro processing has not been disabled within the Microsoft Word application.
Look at Your Extensions!
Files with .EXE or .VBS extensions are always suspect, because once the file name is clicked, the program is run, and it can do anything it wants within the computer. SHS files, a somewhat obscure file type, can also contain executable code. Another approach is to attach a Windows link file (.LNK), which is a shortcut, or pointer, to an executable file (.EXE) that is also attached. Since many have been warned not to click an .EXE attachment, the link file is a sneaky way of launching the .EXE file for unaware users. See
dangerous extensions,
email bomb,
virus,
Klez,
Worm.ExploreZip virus,
BubbleBoy virus and
SHS virus.